Do not connect Hookshot to Redis unless encryption is enabled

It seems like connectivity is problematic, even though the networks
appear to be configured correctly:

> [ioredis] Unhandled error event: Error: connect ECONNREFUSED 172.22.0.2:6739
> at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1595:16)

For now, I disable pointing the queue host to Redis to avoid it.
It should be investigated.

People who enable Hookshot's new experimental encryption may encounter
this also.

Related to spantaleev#3042

group_vars/matrix_servers

@@ -1444,7 +1444,9 @@ matrix_hookshot_systemd_wanted_services_list: |
   }}
 
 # Hookshot's experimental encryption feature (and possibly others) may benefit from Redis, if available.
-matrix_hookshot_queue_host: "{{ redis_identifier if redis_enabled else '' }}"
+# We only connect to Redis if encryption is enabled (not for everyone who has Redis enabled),
+# because connectivity is still potentially troublesome and is to be investigated.
+matrix_hookshot_queue_host: "{{ redis_identifier if redis_enabled and matrix_hookshot_experimental_encryption_enabled else '' }}"
 
 matrix_hookshot_container_additional_networks_auto: |
   {{